A wide-area network (WAN) is a communications network which covers a relatively large geographic area, as compared to a local-area network (LAN). A wireless wide-area network (WWAN) typically employs a cellular radio network to provide wireless communications, possibly on a citywide or even nationwide basis. One illustrative embodiment of a WWAN is a telecommunications network configured according to the GSM (Groupe Spécial Mobile) standard. The GSM standard uses digital channels for both speech and data and, thus, has been referred to as a second generation (2G) mobile telephony system. Third generation (3G) and fourth generation (4G) versions of GSM networks allow simultaneous use of speech and data services at higher data rates than 2G networks. One feature of the GSM standard is the Subscriber Identity Module (SIM), commonly known as a SIM card. A SIM is a detachable smart card that stores an International Mobile Equipment Identity (IMEI) that uniquely identifies the phone or computing device on the GSM network.
Although optimized for telephony, the GSM standard introduced Short Message Service (SMS), or “text messaging,” as an alternate mode of communication between devices on the WWAN. The SMS protocol allows for a “short message” consisting of 140 bytes of data, plus headers and routing information, to be sent over the GSM network. Longer “short messages” may be sent by concatenating several messages together. SMS is realized in modern WWANs by use of the Mobile Application Part (MAP) of the SS7 protocol. A Short Message Service Center (SMSC) is a network element in the WWAN that receives, stores, and forwards (delivers) short messages between user devices on the network.